This invention relates to the assembly of a selected plurality of articles along a substantially fixed distance in an article holder. More particularly, it relates to the assembly of a kit of a selected plurality of articles, including airfoils, about the periphery of a rotating or stationary holder such as a spool, drum, disc, casing, etc.
Power generating apparatus, such as a turbine engine, in one form includes at least one row or stage of blading members which include at least one radially extending airfoil, disposed generally in a row circumferentially about a holder, for example a rotating disc, drum or spool, or a stationary casing. Examples of such members in gas turbine engines are shown in U.S. Pat. Nos. 5,281,087--Hines (patented Jan. 25, 1994); 5,232,339--Plemmons et al. (patented Aug. 3, 1993); and 5,443,365--Ingling et al. (patented Aug. 22, 1995). Such arrangements have been designed for use in various sections of an engine, including the compressor, turbine, and/or fans that have been located in the front or rear sections of the engine. One design of such a holder includes a circumferentially disposed channel or slot at the rim portion of the holder and into which the blading members are placed sequentially during assembly.
It is well known that design of such apparatus, for efficient power production, includes control of gas flow through the apparatus, for example air alone or in combination with products of combustion. To assist in such control, the design includes a specific selected number or plurality of airfoils at various locations in the gas flow stream. For example, each stage or circumferentially disposed row of compressor blading members in a rotating compressor blading member holder, such as a disc, drum or spool, includes a pre-selected number of generally radially outward extending airfoils. The blading members are disposed circumferentially about the holder substantially in a complete circle, allowing a pre-selected tolerance range for the sum of spacing between blades about the circle. To establish such spacing, a portion of each blading member, which includes at least one airfoil, is designed and manufactured for assembly circumferentially about the holder. Such portion, herein called a spacer portion, for example a blade platform or a blade base, has a spacer portion dimension selected to enable such spacing about the holder.
One practice in the design of gas turbine engine compressor blading members and their holders is to select more than one group of blading members, each group having such spacer portion dimension different from the other group, for intermingled distribution of the selected number of members about the holder. For example, a circumferential length of an edge of a compressor blade platform, disposed between a base and an airfoil, represents one type of spacer portion dimension. For the proper assembly of such groups of blading members in a holder, in order to maintain any final gap remaining after assembly within a design tolerance range, it has been a practice first physically to assemble the required number of blading members in the holder to determine a preliminary gap. If the preliminary gap was greater than the tolerance range, or if the sum of the spacer portion dimensions was greater than the space within the holder, a physical, iterative type of substitution of members of one group or the other was conducted until any end gap was within the tolerance range. Such a practice of iterative substitution of blading members in a holder can be time consuming and require inordinately larger supplies of blading members at an assembly location. Typically, blading members are manufactured at one location and such blading members are assembled into a holder at another, sometimes distant, location. Provision, prior to assembly in a holder, of a kit of the articles to fit in the holder within the design tolerance range, and a method for providing such a kit would reduce assembly time and expense.